1. Field of the Invention
The present invention relates to an imaging probe, and more particularly to an imaging probe for detecting photoacoustic image and ultrasound image.
2. Description of the Related Art
Atherosclerotic angiopathies are common diseases, among which the acute ischemic cardiac disease caused by exfoliation of coronary atherosclerotic plaques is the most serious. In order to diagnose and prevent the acute coronary artery disease, it is needed to analyze the structure and the composition of the coronary atherosclerotic plaques.
Currently, intravascular ultrasound imaging technologies are widely used in cardiac microinvasive medical diagnoses. However, an image contrast of soft tissue, fibrous tissue and fat tissue of the plaques provided by a traditional ultrasound image is poor, and thereby exact compositions of the plaques is difficult to be analyzed. Thus, intravascular photoacoustic image is also required. Since absorption coefficients of different compositions of tissues are different, levels of light absorption of different compositions of the tissues are also different, and thereby a contrast of the photoacoustic image is formed. When the tissues irradiated by a pulsed light, the tissues absorb energy and generate thermal expansion effect, then a broadband photoacoustic signal is produced. A receiver receives the photoacoustic signal and converts the photoacoustic signal into an electronic signal. In such way, spatial distributions of the compositions of the tissues are showed by the photoacoustic image.
The photoacoustic image simultaneously has a high contrast of optical image and a deeper penetration depth of ultrasound image. Additionally, the photoacoustic image can provide functional information of the tissues. The ultrasound image can provide structural information of the tissues. Therefore, a stenosis of blood vessel, compositions and positions of the atherosclerotic plaques can be effectively assessed via a combination of the photoacoustic image and the ultrasound image. As a result, the exfoliation risk of the plaques can be assessed, so that an appropriate treatment can be selected to prevent the acute ischemic cardiac disease.
In traditional technology, when an imaging probe is used to obtain the photoacoustic image, the pulsed light energy irradiates along a single direction through a fiber. In order to obtain the intravascular photoacoustic image, a mechanical scanning method is used to obtain a complete image. The mechanical scanning method comprises rotating the imaging probe in the blood vessel so as to obtain a plurality of fragments of the photoacoustic image. Then, the fragments of the photoacoustic image are pieced together to a circled photoacoustic image of the blood vessel. Thus, the imaging probe is required to rotate a lap to obtain a complete photoacoustic image, which is a waste of time and is unable to achieve a function of real-time imaging.